[penragonwebsite]

[macman104]

Can you show us how you solved it?

[penragonwebsite]

I only solved it on paper and its long so its hard to transfer to the computer but I can say what I did.

I first found the molar mass of the compound by using PM=dRT. Then I found the volume at STP using the combined gas law using the values for the carbon. Then I found the mass using m= d x v. Then I found the volume of Hydrogen assuming that it was at STP using v= m/d. I took that volume and used n= Vstp/Mv to find n. Then I used the n value and multiplied it by 2.02 for hydrogen, considering the fact that water is H₂O, so there should be 2 H's. Then I converted the masses into mg and subtracted them from the overall mass of 18.9 mg. From there I found the number of moles using the mass for each, and then I found the mole ratio using the mole value for O. Using those I came out with a EF of CH₇O. Using the molar mass I found at the start, I subtracted the molar mass of the EF from it and it equaled to about 2. So using that I got the value for the MF to be C₂H₁₄O₂.

I really had no idea what to do, so I just tried what I knew...

[nj_bartel]

Something you always want to do is check the reasonableness of your answer.  The molecular formula you provided is very obviously an impossible compound, as a fully saturated 2 carbon 2 oxygen molecule can form a max of 6 bonds (6 hydrogens).

[vhpk]

Huh, something is wrong with your answer.
Firstly, use the ideal gas equation to calculate the Mr of your compound, it will be 88(g/mol)
So, using this relative mass, you can calculate the moles of 18,9mg of the compound.
Continue using the ideal gas equation to calculate the moles of carbondioxide and infer the number of C
The moles of water help you about the number of H
After all, you get the number of O and the formula.
Try again and good luck

[Donaldson Tan]